Ultrasonic Input Device With Segmented Transceivers
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Solution Overview
Problem
Ultrasonic pulse echo rangefinding systems face interference issues when objects are close to the transceiver, leading to inaccurate time-of-flight measurements and position tracking due to direct feedthrough of the acoustic signal from the transmitter to the receivers.
Innovation Solution
The system employs multiple ultrasonic transceivers with synchronized operation, using MEMS transducers and signal processing techniques such as moving average filters to differentiate between direct feedthrough and target echoes, allowing for accurate position calculation and wide field-of-view operation without phased arrays, which reduces complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ultrasonic transceiver is used to transmit and detect echoes, then device complexity is reduced, but measurement precision deteriorates due to interference between transmitted pulses and return echoes when objects are close
Solution Approach 1:
The system divides the transceiver function into separate transmit and receive transducers. The transmit transducer sends ultrasonic pulses while receive transducers detect echoes, preventing self-interference. This segmentation allows accurate ToF measurement even for close objects by eliminating the feedthrough problem inherent in single transceiver designs.
Solution Approach 2:
The harmful direct feedthrough signal is extracted and separated from the useful echo signal through spatial separation of transmit and receive transducers. By placing receive transducers at different locations than the transmit transducer, the system isolates the weak echo signals from the strong transmitted pulse interference.
2Measurement precision
If multiple transceivers are used to determine position in 2 or 3 dimensions, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system combines multiple receive transducers with a single transmit transducer into a coordinated measurement system. All receive transducers operate simultaneously to detect echoes from the same transmitted pulse, enabling 2D or 3D position determination through triangulation while sharing a common transmit source, thus reducing overall system complexity compared to using multiple independent transceivers.
3Device complexity
If the same transceiver is used for both transmission and detection, then device complexity is minimized, but reliability deteriorates due to signal interference preventing accurate ToF measurement
Solution Approach 1:
The transceiver function is segmented into dedicated transmit and receive transducers. This segmentation ensures that the transmitted pulse and received echo are spatially separated, eliminating self-interference and ensuring reliable ToF measurements even for objects in close proximity.
Solution Approach 2:
The system uses signal processing techniques including moving average filters as intermediaries to further separate the useful echo signal from residual interference. The filter acts as a mediator that enhances the reliability of echo detection by suppressing noise and feedthrough artifacts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate detection and tracking of objects in a wide field of view with reduced interference, maintaining low power consumption and simplicity, even at close proximity to the transceivers, and supports both continuous and quantized position reporting.
Implementation Method 1
Ultrasonic pulse echo rangefinding is used to detect nearby objects. Ultrasonic pulse-echo measurements bounce sound off the object and measure the time-of-flight (ToF) of the echo.
Implementation Method 2
The ToF can be converted into round-trip range by multiplying by the speed of sound.
Implementation Method 3
The transducer units may include piezoelectric or capacitive micromachined ultrasonic transducers
Implementation Method 4
The transducer units may include piezoelectric or capacitive micromachined ultrasonic transducers
Data Source
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AI summary
An ultrasonic input includes two or more ultrasonic transceiver units having transducers separated from each other by a predetermined spacing and a processor coupled to the transceiver units. In some implementations one unit transmits while two receive and in other implementations one unit transmits and receives while the other just receives. The transmitter sends an ultrasonic pulse and first and second receivers receive echoes of the ultrasonic pulse from an object. The processor and/or transceiver units perform moving average filtering of receive signals, continuously update the moving averages, subtract the updated moving averages from the receive signals to produce filtered receive signals, and determine first and second time-of-flight measurements corresponding to times between transmitting the pulse and receiving an echo of the pulse by the first and second receivers, respectively using the filtered receive signals